Modern footwear is available in a myriad of materials and fabrications. Despite great advances in support, there has been relatively little development in thermal management of footwear. Very few shoes have been designed to provide methods of dissipating heat generated by the foot from inside the shoe. The foot generates heat while walking, running, or even at rest. As heat is generated by the foot, the shoe temperature begins to rise, and the foot begins to perspire. Excessive perspiration around the foot leads to foot and shoe odor among other problems.
Specifically, the heat and perspiration released by the foot causes several problems. A wet and warm shoe interior is uncomfortable for the user to wear. Further, the perspiration released by the foot contains sodium chloride and urea, which can stain or discolor the outer surface of the shoe, degrading the expressive value of the shoe to the wearer. Moreover, the perspiration and heat around the foot creates an ideal environment for fungi and bacteria to thrive. Fungi and bacteria consume dead skin cells, and produce waste that is the source of foot odor. Fungi and bacteria convert the amino acid methionine to methanethiol which has a sulfuric smell. One such bacteria in the foot is brevibacteria, the same bacteria that gives cheeses such as Limburger, Bel Paese, Port du Salut, and Munster their characteristic pungency. As physical activity increases, foot perspiration, bacterial growth, and bacterial waste production all increase, causing odor to intensify. Finally, a warm and moist shoe provides an ideal environment for foot disease, such as Athlete's foot, to thrive.
One approach minimizing the problems stated above is to provide shoe ventilation to transfer heat and moisture away from the foot. The theory behind shoe ventilation is to reduce the interior temperature and humidity of the shoe by transferring heat and foot perspiration generated by the foot away from the interior of the shoe. Since perspiration decreases with decreasing temperature, a decrease in the interior temperature of the shoe decreases the rate of perspiration around the foot. Thus, the goal of shoe ventilation is to maintain an interior shoe temperature as close to the ambient air temperature as possible. By forcing ambient air around the foot and into the shoe cavity, heat and moisture generated by the foot is transferred away from the foot by the circulating air.
Past disclosures have provided footwear systems for ventilating the area under the foot. These systems are directed towards a pumping system in the sole of the shoe that is actuated by foot movement during walking or running. For example a pump draws ambient air into a cavity in the sole of the shoe, circulates the air within the sole, and then expels it through the sole back into the atmosphere. In another variation, the pump expels the air into the interior of the shoe through ports in the sole. While these systems help transfer excess heat away from the bottom of the foot surface they are ineffective because they do not transfer heat away from the top, rear, and sides of the foot. This allows excessive heat and moisture to build up inside the shoe.
It is possible to make a shoe upper out of mesh or another relatively breathable material, however, these constructions are only suitable for certain types of running shoes or water shoes, and are not appropriate for street shoe constructions or office wear.
Some representative examples of conventional footwear ventilation systems are described below.
U.S. Application No. 2006/0032083 to Lim is directed towards a shoe with a ventilation port in the front of the shoe that communicates with the interior of the shoe, thus allowing for a circulation of air into and from the interior of the shoe while a user walks. An elastic pumping device on the heel of the shoe draws ambient air into the shoe from an intake port in the toe of the shoe to a cavity in the sole of the shoe. This air is then expelled into the interior of the shoe through a hole in the insole. However this system is ineffective at providing adequate circulation to transfer heat away from the foot. The system does not remove heat from the sides, rear, and top of the foot. Second, this system does not provide an efficient means for exhausting the contaminated air. While ambient air is forced inside the shoe through holes in the sole, the bottom of the foot, which rests on top of the insole, prevents or reduces air flow to the interior of the shoe.
U.S. Pat. No. 6,076,282 to Brue is directed towards a forced ventilation shoe that increases the efficiency of the actuated pumping system. The midsole and outsole of the shoe have a series of occluding holes that prevent the return of contaminated air from the sole cavity back into the interior shoe cavity. However, this system is ineffective at providing adequate heat transfer away from the foot because it does not remove heat from the sides, rear, and top of the foot. Second, the downward pressure of the foot prevents ambient air from entering the shoe cavity.
U.S. Pat. No. 6,305,100 to Komarnycky et al. discloses a cavity in the sole of the shoe formed by a series of ridges in the outsole and insole. The lateral surfaces of the sole contain valves that facilitate bidirectional air circulation. However, this system is ineffective at providing adequate heat transfer away from the foot because it does not remove heat from the sides, rear, and top of the foot. Second, the downward pressure of the foot prevents ambient air from entering the shoe cavity. Third, this system recirculates contaminated air from the sole cavity back into the interior of the shoe, resulting in increased foot temperature.
U.S. Pat. No. 5,400,526 to Sessa is directed towards a footwear sole with bulbous protrusions and pneumatic ventilation. Sessa discloses a shoe sole with a forced ventilation system. The system exchanges ambient air from the side of the sole, through a cavity and pumping mechanism in the sole, into the cavity of the shoe, underneath the user's foot. Sessa uses bulbous protrusions on the top-side of the insole to prevent air holes from becoming blocked by the downward pressure of the foot. However, this system does not provide adequate heat removal because it does not transfer heat from the sides, rear, and top of the foot.